Hi readers for a balanced pre-amp:
I would just like to show the availability of my latest RelaiXed design: a renewed implementation on a more compact PCB due employing more SMD components:
- 4 single-ended and 4 balanced inputs, balanced outputs
- The metal-can LME49720 opamps provide really good sound.
- No 'plastic' capacitors in the signal path (only a Mica for high-frequency decoupling)
- very low-noise/clean powersupply for these opamps
- volume and balance control through relays and remote control
- PIC microcontroller software is open-sourced, controls amplifier board through I2C
see: RelaiXedSMD -- Documentation

Hi,
Please consider this simple SE to Balanced circuit...
THD is very good. 2Vrms@10kHz into 22k = 0.004% THD. (analyzed on one output)
...The NPN can be almost any standard transistor: BC546

Well-done! Indeed, good results are obtainable with few transistors, and higher power-supply voltages do help. The tiny (1%) imbalance on your outputs would be negligible in practice, results from the transistor Hfe, and would vanish when applying a Fet. It would be nice to see as comparison your distortion-figures when a Fet is inserted. Which circuit analysis program is this?